Atopic diseases, including atopic dermatitis, asthma, allergic rhinitis, and allergic conjuctivitis, are pathological conditions which permit the subject's own immune system to destroy, and cause disturbance of organs as a result of hyper-responses to environmental antigens to which healthy subjects usually exhibit no response. A conceivable mechanism of development of these diseases includes contribution of Th2 cytokine, which promotes allergic responses. The induction mechanism and regulatory mechanism, which are crucial from the physiological and pharmacological viewpoints, have not yet been completely elucidated.
At present, mainstream treatments of atopic diseases include avoidance of antigens; administration of antihistaminic agents which serve as antagonists against binding of a mediator such as histamine to a receptor; and administration of anti-inflammatory steroids. However, development of improved therapies targeting more specific action mechanisms remains hindered, because no suitable test animals have been provided.
According to conventional techniques, in order to elicit an allergic response from a test animal, the animal must first be sensitized through repeated immunization of an antigen or an allergen in advance, and then be challenged with the same type of antigen or the allergen. Such a process not only imposes considerable workload for simultaneously sensitizing numerous animals, but also produces non-uniformity between animals in terms of reactivity, raising potential problems on reproducibility of the test.
In recent years, NC/Nga mice have attracted attention for their potential use as an animal model of atopic dermatitis. However, this dermatitis is developed only in the case where the host mouse carries a mite, and further, the percent onset is inconsistent and symptoms develop in different forms.
Tests using animals are indispensable in the development of remedies for atopic diseases, and in particular, demand exists for animal models of atopic dermatitis. To date, however, no such animal models of atopic dermatitis having a well-established hereditary background and clarified immunological traits and being available for research and development of remedies and pharmaceuticals under conditions from which specific pathogenic microorganisms are eliminated have ever existed or put into practical use.
Accordingly, an object of the present invention is to create an animal that is useful as an atopic dermatitis model.